1. Technical Field
The invention relates to mechanical clocks. More particularly, the invention relates to a mechanical device for converting one time base to another.
2. Description of the Prior Art
A clock which displays multiple intervals, such as hours and days, requires a mechanism for converting the basic time base, such as the wing of a pendulum, into the displayed intervals, e.g. hours. This is normally accomplished with a gear train, which works well when the intervals displayed are integer multiples of the period of the time base. However, such integral multiple relationship is not achievable when the displayed intervals do not bear a simple rational relationship to one another. This is the case, for example, when the intervals displayed are constants, such as lunar months and solar years, which are approximately 29.5303882 days and 365.242198 days, respectively. The calendar is arranged to add a day each fourth year to compensate roughly for this mismatch between the calendar year and the solar year, i.e. an extra day is added to the month of February during leap years. Such factors are also readily taken into account with electronic time keeping systems. However, in a mechanical clock that uses a gear train, these constants must be approximated by a ratio of numbers. If conventional mechanical techniques are used, a gear train having a very large number of gear teeth is required to achieve an accurate approximation of such constants.
It would be advantageous to provide a mechanical device that achieves an accurate approximation of such constants as lunar months and solar years without requiring a complex gear train, e.g. a gear train having a very large number of gear teeth.